<?php
 $username=$_POST['username'];

 $conn = mysqli_connect("localhost","root","root","db21130928");
 if(!$conn){
     echo "不好意思，我没连上数据库";
 }else{
    
     $sqlStr = "select * from vip where username='$username'";

     $result = mysqli_query($conn,$sqlStr);

     // 3、关闭数据库
     mysqli_close($conn);

     if(mysqli_num_rows($result)>0){
         // 三、响应
         echo 0;
     }else{
         // 三、响应
         echo 1;
     }
     
 }
?>